Connection control device, communication system and connection control method

Abstract

To suppress an increase in processing load while preventing deterioration of communication quality.SOLUTION: A connection control device includes an acquisition unit that acquires information on received power from each of a plurality of wireless devices in a plurality of terminal devices, an aggregation unit that aggregates estimated communication loads in the plurality of wireless devices using the received power information respectively, a determination unit that determines a wireless device belonging to each of a plurality of cells on the basis of an index indicating the distribution of processing load for each cell corresponding to the estimated communication load of the wireless devices in the cell, and a generation unit that generates connection control information for connecting a baseband processing device that manages a cell and a wireless device that belongs to the cell.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a connection control device, a communication system, and a connection control method. [Background technology]

[0002] In recent years, in wireless communication systems, a distributed antenna system (DAS) is becoming more widespread, in which a base station device is separated into a baseband unit (BBU) and a radio unit (RU), and a number of RUs connected to the BBU are distributed to form a cell for each BBU. The BBU is a baseband processing device that performs baseband processing on signals, and the RU is a wireless device equipped with an antenna that performs wireless processing on signals.

[0003] In a DAS, multiple RUs can be arranged relatively freely to form cells, so DAS-based multipoint communication is also effective for wireless communications that use high-frequency bands that are difficult to penetrate through obstructions, such as the millimeter waves used in the fifth generation mobile communications system (5G). If a terminal device can transmit and receive radio waves to any one of the multiple RUs that form a cell, it can communicate with the BBU that forms this cell. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2012-169741 A [Patent Document 2] JP 2013-090039 A [Patent Document 3] JP 2013-077965 A Summary of the Invention [Problem to be solved by the invention]

[0005] However, since the distribution of wireless communication traffic volume changes depending on the time of day, there is a problem that the traffic volume for each cell and RU becomes uneven, which may increase the processing load on the BBU.

[0006] For example, when a cell is congested and many terminal devices are concentrated in the cell, the BBU corresponding to the cell is overloaded. In such a case, it is possible to reduce the processing load of the BBU corresponding to the cell by making some of the terminal devices that wirelessly communicate with the RU of the cell wirelessly communicate with the RU of an adjacent cell. However, since some of the terminal devices are connected to the adjacent cell, the communication quality of these terminal devices deteriorates, and the throughput of the entire system decreases.

[0007] The disclosed technology has been developed in consideration of these points, and aims to provide a connection control device, a communication system, and a connection control method that can prevent deterioration of communication quality while suppressing an increase in processing load. [Means for solving the problem]

[0008] In one aspect, the connection control device disclosed in the present application has an acquisition unit that acquires information on received power from each of multiple radio devices in multiple terminal devices, an aggregation unit that uses the received power information to aggregate estimated communication loads in each of the multiple radio devices, a determination unit that determines a radio device that belongs to each of multiple cells based on an index indicating a distribution of processing loads for each cell corresponding to the estimated communication loads of the radio devices in the cell, and a generation unit that generates connection control information to connect a baseband processing device that manages the cell to the radio devices that belong to the cell. Effect of the Invention

[0009] According to one aspect of the connection control device, communication system, and connection control method disclosed in the present application, it is possible to suppress an increase in the processing load while preventing a deterioration in communication quality. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 is a diagram illustrating an example of the configuration of a wireless communication system. [Diagram 2] FIG. 2 is a block diagram showing a configuration of the connection control device according to the first embodiment. [Diagram 3] FIG. 3 is a flow diagram showing a connection control method according to the first embodiment. [Figure 4] FIG. 4 is a flow diagram showing the parent RU selection process. [Diagram 5] FIG. 5 is a flow diagram showing the child RU determination process. [Figure 6] FIG. 6 is a block diagram showing a configuration of a connection control device according to the second embodiment. [Figure 7] FIG. 7 is a flow diagram showing a connection control method according to the second embodiment. [Figure 8] FIG. 8 is a flow diagram showing the interference score calculation process. [Figure 9] FIG. 9 is a flow diagram showing the parent RU selection process. [Figure 10] FIG. 10 is a block diagram showing a configuration of a connection control device according to the third embodiment. [Figure 11] FIG. 11 is a flow diagram showing a connection control method according to the third embodiment. [Figure 12] FIG. 12 is a flow diagram showing the parent RU selection process. [Figure 13] FIG. 13 is a flowchart showing the child RU determination process. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, embodiments of a connection control device, a communication system, and a connection control method disclosed in the present application will be described in detail with reference to the drawings. Note that the present invention is not limited to the embodiments.

[0012] (Embodiment 1) 1 is a diagram showing an example of the configuration of a wireless communication system according to the first embodiment. This wireless communication system is configured by connecting a plurality of baseband processing devices 10-1 to 10-M (M is an integer equal to or greater than 2) and a plurality of radio devices (RUs: Radio Units) 20 via a connection switching device 50. The baseband processing device 10-1 manages a cell 25-1 formed by the connected RUs 20, the baseband processing device 10-2 manages a cell 25-2 formed by the connected RUs 20, and similarly, the baseband processing device 10-M manages a cell 25-M formed by the connected RUs 20.

[0013] A terminal device 30 located in any one of the cells 25-X (X is 1 to M) wirelessly communicates with an RU 20 in the cell 25-X, and transmits and receives data to and from a baseband processing device 10-X that manages the cell 25-X. The terminal device 30 measures the received power at a predetermined period using a reference signal transmitted from the RU 20, and reports information on the measured received power to the baseband processing device 10-X that manages the cell 25-X in which the terminal device 30 is located. At this time, the terminal device 30 measures the received power not only from the RU 20 with which it wirelessly communicates, but also from other RUs 20 in the cell 25-X and RUs 20 in other cells 25-1 to 25-M, and transmits received power information for each RU 20 to the baseband processing device 10-X via the RU 20 with which it wirelessly communicates.

[0014] The connection relationship between the baseband processing devices 10-1 to 10-M and the RU 20 can be switched by a connection switching device 50. A connection control device 100 is connected to the connection switching device 50, and the connection control device 100 controls the connection between the baseband processing devices 10-1 to 10-M and the RU 20 based on the reception power at the terminal device 30.

[0015] That is, the connection control device 100 collects reception power information for each RU 20 in the terminal devices 30 from the baseband processing devices 10-1 to 10-M, and estimates the terminal devices 30 (hereinafter also referred to as "connected terminals") that communicate wirelessly with each RU 20 based on the collected reception power information. Then, based on the connected terminals for each RU 20, the connection control device 100 determines the RUs 20 to be connected to each of the baseband processing devices 10-1 to 10-M so as to reduce the variation in processing load for each cell 25-1 to 25-M. The connection switching device 50 switches the connections between the baseband processing devices 10-1 to 10-M and the RUs 20 in accordance with the connection relationships between the baseband processing devices 10-1 to 10-M and the RUs 20 determined by the connection control device 100.

[0016] Fig. 2 is a block diagram showing the configuration of the connection control device 100 according to embodiment 1. The connection control device 100 shown in Fig. 2 includes a communication interface unit (hereinafter abbreviated as "communication I / F unit") 110, a processor 120, a memory 130, and a connection control information transmission unit 140.

[0017] The communication I / F unit 110 is an interface that is wired and connected to the baseband processing devices 10-1 to 10-M and communicates with the baseband processing devices 10-1 to 10-M. The communication I / F unit 110 receives the reception power information for each RU 20 reported from each terminal device 30 from the baseband processing devices 10-1 to 10-M.

[0018] The processor 120 includes, for example, a CPU (Central Processing Unit), an FPGA (Field Programmable Gate Array), or a DSP (Digital Signal Processor), and generally controls the entire connection control device 100. Specifically, the processor 120 includes a received power collecting unit 121, a connected terminal counting unit 122, a parent RU selecting unit 123, a child RU determining unit 124, and a connection control information generating unit 125.

[0019] The received power collecting unit 121 collects the received power for each RU 20 of each terminal device 30 from the received power information received by the communication I / F unit 110. For each terminal device 30, the received power collecting unit 121 collects not only the RU 20 with which the terminal device 30 wirelessly communicates, but also the received power of other RUs 20 in the cell in which the terminal device 30 is located and RUs 20 in other cells. In other words, for each terminal device 30, the received power collecting unit 121 collects the received power from all RUs 20 from which the terminal device 30 can receive reference signals.

[0020] The connected terminal counting unit 122 counts the received power from the RU 20 for each terminal device 30, and estimates the connected terminal for each RU 20. Specifically, the connected terminal counting unit 122 identifies the RU 20 with the maximum received power for each terminal device 30, and estimates that each terminal device 30 is a connected terminal of the identified RU 20. The connected terminal counting unit 122 then counts the number of connected terminals for each RU 20. Since the number of connected terminals corresponds to the communication load of the RU 20, it can be said that the connected terminal counting unit 122 counts the estimated communication load on each RU 20 when a connected terminal is connected.

[0021] The parent RU selection unit 123 selects a parent RU for each of the cells 25-1 to 25-M based on the counting result by the connected terminal counting unit 122 and the location information of each RU 20. Specifically, the parent RU selection unit 123 first selects the RU 20 with the largest number of connected terminals as the parent RU of one cell (e.g., cell 25-1). Then, the parent RU selection unit 123 selects the RU 20 with the greatest distance from the selected parent RU as the parent RU of the next cell (e.g., cell 25-2). Furthermore, the parent RU selection unit 123 selects the RU 20 with the largest sum of distances from the selected parent RU as the parent RU of the next cell (e.g., cell 25-3). In this way, the parent RU selection unit 123 selects the RU 20 with the largest number of connected terminals as the first parent RU, and then sequentially selects the RU 20 with the largest sum of distances from the selected parent RU as the parent RU, thereby selecting M parent RUs corresponding to the cells 25-1 to 25-M.

[0022] The child RU determination unit 124 calculates an index of the variation in the number of connected terminals of the cell, and determines child RUs that belong to the same cell as each of the M parent RUs so that this index is small. Specifically, the child RU determination unit 124 selects a cell (e.g., cell 25-Y) with the smallest number of connected terminals, and identifies adjacent RUs adjacent to RU 20 that already belong to this cell 25-Y. Then, the child RU determination unit 124 calculates an index of the dispersion of the number of connected terminals of the cell when the adjacent RU is added to cell 25-Y, and determines the adjacent RU that minimizes this index as the child RU of cell 25-Y. Note that the "number of connected terminals of a cell" refers to the total number of connected terminals of all RUs 20 that belong to the cell. For the cell with the smallest number of connected terminals, the child RU determination unit 124 determines one adjacent RU that minimizes the dispersion index of the number of connected terminals of the cell as the child RU, and repeats the determination of child RUs until all RUs 20 belong to one of the cells.

[0023] The connection control information generation unit 125 generates connection control information for connecting the RU 20 for each of the cells 25-1 to 25-M to the baseband processing devices 10-1 to 10-M, based on the parent RU selected by the parent RU selection unit 123 and the child RU determined by the child RU determination unit 124. That is, the connection control information generation unit 125 generates connection control information for connecting the parent RU and child RU belonging to the cell 25-1 to the baseband processing device 10-1, for connecting the parent RU and child RU belonging to the cell 25-2 to the baseband processing device 10-2, and so on, connecting the parent RU and child RU belonging to the cell 25-M to the baseband processing device 10-M.

[0024] The memory 130 includes, for example, a random access memory (RAM) or a read only memory (ROM), and stores information used in processing by the processor 120.

[0025] The connection control information transmitter 140 transmits the connection control information generated by the connection control information generator 125 to the connection switching device 50. As a result, the connection switching device 50 switches the connections between the baseband processing devices 10-1 to 10-M and the RUs 20 in accordance with the connection control information so that the RUs 20 belonging to the cells 25-1 to 25-M are connected to the corresponding baseband processing devices 10-1 to 10-M, respectively.

[0026] Next, a connection control method by the connection control device 100 configured as above will be described with reference to the flow chart shown in FIG.

[0027] Each terminal device 30 in the wireless communication system measures the received power of a reference signal from each RU 20 at a predetermined period, and reports received power information indicating the received power of each RU 20 to the baseband processing devices 10-1 to 10-M corresponding to its own cell. The received power information reported from each terminal device 30 is transmitted from the baseband processing devices 10-1 to 10-M to the connection control device 100, and received by the communication I / F unit 110 of the connection control device 100. Then, the received power for each RU 20 in each terminal device 30 is collected by the received power collection unit 121 (step S101).

[0028] The received power of each terminal device 30 is used by the connected terminal counting unit 122 to count the connected terminals. That is, the connected terminal counting unit 122 identifies the RU 20 with the maximum received power for each terminal device 30, and each terminal device 30 is estimated to be a connected terminal of the identified RU 20. Then, the connected terminal counting unit 122 counts the number of connected terminals for each RU 20 (step S102).

[0029] Once the number of connected terminals for each RU 20 has been tallied, parent RU selection unit 123 selects parent RUs in the same number as cells 25-1 to 25-M (step S103). That is, parent RU selection unit 123 selects M parent RUs based on the number of connected terminals for each RU 20 and their location information. Parent RU selection is performed by selecting the RU 20 with the largest number of connected terminals as the first parent RU, and thereafter selecting the RU 20 with the largest sum of distances from the previously selected parent RUs as the next parent RU. The parent RU selection process will be described in detail later.

[0030] Once M parent RUs are selected, child RU determination unit 124 determines child RUs that belong to the same cell as these parent RUs (step S104). That is, child RU determination unit 124 calculates a dispersion index for the number of terminals connected to the cell when an adjacent RU is added to the cell, and determines the adjacent RU that minimizes the dispersion index as the child RU. The determination of child RUs is repeated until all RUs 20 belong to one of the cells. The child RU determination process will be described in detail later.

[0031] Because all of the RUs 20 belong to one of the cells 25-1 to 25-M as a result of the parent RU selection process and the child RU determination process, the connection control information generator 125 generates connection control information for connecting the baseband processing devices 10-1 to 10-M to the RUs 20 that belong to the cells 25-1 to 25-M (step S105). The generated connection control information is transmitted from the connection control information transmitter 140 to the connection switching device 50 (step S106), and the connection switching device 50 switches the connections between the baseband processing devices 10-1 to 10-M and the RUs 20 in accordance with the connection control information.

[0032] In this way, the terminal device 30 is set as the connection terminal of the RU 20 with the maximum received power respectively, the RU 20 belonging to each cell is determined so that the dispersion index of the number of connection terminals of the cell is minimized, and the connection relationship between the baseband processing devices 10-1 to 10-M corresponding to the cell and the RU 20 is controlled. For this reason, the communication quality of the terminal device 30 does not deteriorate, the variation in the number of connection terminals per cell becomes small, and the processing loads of the baseband processing devices 10-1 to 10-M are averaged. In other words, it is possible to suppress an increase in the processing load of the baseband processing devices 10-1 to 10-M while preventing deterioration of the communication quality in the terminal device 30.

[0033] Next, the parent RU selection process will be specifically described with reference to the flowchart shown in FIG. 4. The following processes are executed by the parent RU selection unit 123.

[0034] First, the parent RU of the first cell is selected from the number of connection terminals for each RU 20. That is, the RU #r (r is the identification information of the RU 20) that satisfies the following formula (1) is selected as the first parent RU #1 (step S201).

Equation

[0035] However, in formula (1), N UE (r’) is the number of connection terminals of the RU #r’, and argmax[P(x)] is a function that returns the variable x that maximizes P(x). Therefore, the right side of formula (1) returns r’ for which the number of connection terminals N UE (r’) is the largest. When the RU #r determined by formula (1) is selected as the first parent RU #1, the following processes are repeated according to the number of cells. Here, since the first parent RU #1 of the first cell is selected, the following processes are repeated for the remaining (M−1) cells.

[0036] That is, for the c-th cell #c (1 < c ≤ M), the RU #r that satisfies the following formula (2) is selected as the parent RU #c (step S202).

Equation

[0037] In equation (2), s is the identification information of the parent RU of the other cell that has already been selected, D r’s indicates the distance between RU#r' and RU#s. The distance between RU#r' and RU#s can be calculated from the position information of each RU 20. The right side of formula (2) is the distance D r’s The process returns r' that maximizes the sum of the distances between the RUs. The process of selecting RU#r determined by formula (2) as the parent RU#c of cell#c is repeated, and a parent RU is selected for each of the M cells 25-1 to 25-M. These parent RUs are placed at positions that maximize the sum of the distances between them.

[0038] Next, the child RU determination process will be specifically described with reference to the flow diagram shown in Fig. 5. The following process is executed by the child RU determination unit 124.

[0039] Here, since the parent RUs of the M cells have already been selected, a cell #c (c is cell identification information) is selected from these cells by the following formula (3) (step S301).

number

[0040] In formula (3), N UE (c') is the number of connected terminals in cell #c', and argmin[P(x)] is a function that returns the variable x that minimizes P(x). The number of connected terminals in cell #c' is the total number of connected terminals in all RUs 20 that belong to cell #c'. The right-hand side of the above formula (3) is the number of connected terminals N UEWhen cell #c with the smallest number of connected terminals is selected according to formula (3), a list Nei(c) of RUs adjacent to cell #c is generated (step S302). Specifically, of the RUs 20 that do not belong to any cell, those RUs 20 that are adjacent to any RU 20 in cell #c are added to list Nei(c). At this time, it is possible to determine whether an RU 20 is adjacent from the location information of the RU 20.

[0041] Once the list Nei(c) of neighboring RUs of cell #c is generated, the following process is repeated for each neighboring RU included in the list Nei(c) of cell #c.

[0042] That is, one neighboring RU#r included in list Nei(c) is provisionally added to cell #c (step S303), and the dispersion index V(r) of the number of connected terminals in each cell when this neighboring RU#r is added to cell #c is calculated by the following equation (4) (step S304).

number

[0043] In formula (4), N cell is the number of cells (here M), N UE (c, r) indicates the number of connected terminals of cell #c when an adjacent RU #r is added to cell #c. The dispersion index V(r) calculated by formula (4) is an index of the variation in the number of connected terminals of each cell when one adjacent RU #r is added to cell #c. Since the number of connected terminals of a cell is an index of the processing load of the baseband processing device corresponding to this cell, the dispersion index V(r) is also an index of the variation in the processing load of baseband processing devices 10-1 to 10-M.

[0044] In this way, when the dispersion index V(r) when adding adjacent RU #r to cell #c is calculated for each adjacent RU included in list Nei(c), adjacent RU #r that satisfies the following equation (5) is added as a child RU of cell #c (step S305).

number

[0045] That is, the neighboring RU #r that minimizes the dispersion index V(r) when added to cell #c is added to cell #c as a child RU. This means that neighboring RUs are added to cells so that the number of connected terminals per cell is equalized as much as possible. Then, it is determined whether all RUs 20 have been added to any cell as child RUs (step S306), and if there is an RU 20 that does not yet belong to any cell (step S306 No), the process is repeated from step S301 in which cell #c with the smallest number of connected terminals is selected.

[0046] Through the above child RU determination process, all RUs 20 belong to one of the cells, and the variation in the number of connected terminals for each cell is minimized. That is, the number of connected terminals for each cell is averaged, and no baseband processing devices 10-1 to 10-M will have an excessive processing load. In other words, an increase in the processing load of the baseband processing devices 10-1 to 10-M can be suppressed.

[0047] As described above, according to the present embodiment, the RUs belonging to each cell are determined so that the variation in the number of connected terminals for each cell is minimized, with each terminal device being treated as a connected terminal of the RU with the maximum received power. Therefore, it is possible to average the number of connected terminals for the cells corresponding to each of the multiple baseband processing devices without deteriorating the communication quality of the terminal device, thereby suppressing an increase in the processing load of the baseband processing devices.

[0048] (Embodiment 2) The feature of the second embodiment is that, instead of determining the neighbor relationships between RUs using location information of the RUs, the neighbor relationships between RUs are determined using interference scores between the RUs.

[0049] The configuration of the wireless communication system according to the second embodiment is similar to that of the first embodiment (FIG. 1), and therefore a description thereof will be omitted.

[0050] Figure 6 is a block diagram showing the configuration of a connection control device 100 according to embodiment 2. In Figure 6, the same components as those in Figure 2 are given the same reference numerals, and their explanation will be omitted. The connection control device 100 shown in Figure 6 has a configuration in which an interference score calculation unit 201 is added to the connection control device 100 shown in Figure 2, and a parent RU selection unit 202 and a child RU determination unit 203 are provided instead of parent RU selection unit 123 and child RU determination unit 124.

[0051] The interference score calculation unit 201 calculates an interference score for each pair of RUs 20 based on the received power at the terminal devices 30. Specifically, the interference score calculation unit 201 calculates the number of terminal devices 30 for which the difference in received power from each of the two RUs 20 constituting a pair is less than a predetermined threshold as the interference score of the pair of RUs 20. The interference score calculation unit 201 calculates interference scores for all combinations of pairs of RUs 20. A terminal device 30 for which the difference in received power from the two RUs 20 is small is considered to be located at approximately the same distance from the two RUs 20. Therefore, if there are many terminal devices 30 for which the difference in received power is less than a predetermined threshold, it is highly likely that the two RUs 20 are located close to each other. Therefore, a pair of RUs 20 with a high interference score can be considered to be a pair of RUs 20 adjacent to each other.

[0052] Parent RU selection unit 202 selects a parent RU for each of cells 25-1 to 25-M based on the counting result by connected terminal counting unit 122 and the interference scores of each RU 20 pair. Specifically, parent RU selection unit 202 first selects the RU 20 with the largest number of connected terminals as the parent RU of one cell (e.g., cell 25-1). Parent RU selection unit 202 then selects the RU 20 with the smallest interference score with the already selected parent RU as the parent RU of the next cell (e.g., cell 25-2). Furthermore, parent RU selection unit 202 selects the RU 20 with the smallest sum of interference scores with each of the already selected parent RUs as the parent RU of the next cell (e.g., cell 25-3). In this way, parent RU selection unit 202 selects RU 20 with the largest number of connected terminals as the first parent RU, and then sequentially selects RU 20 with the smallest sum of interference scores paired with an already selected parent RU as the parent RU, thereby selecting M parent RUs corresponding to cells 25-1 to 25-M.

[0053] Child RU determination unit 203 calculates an index of variation in the number of connected terminals in a cell, and determines child RUs that belong to the same cell as each of the M parent RUs so that this index is small. Specifically, child RU determination unit 203 selects a cell with the smallest number of connected terminals (e.g., cell 25-Y), and identifies adjacent RUs adjacent to RU 20 that already belongs to cell 25-Y. At this time, child RU determination unit 203 identifies adjacent RUs using an interference score for each pair of RUs 20. Here, for a pair of RU#r that already belongs to cell 25-Y and RU#s that does not yet belong to any cell, the interference score I rs RU#r and RU#s are adjacent if they satisfy the following condition (A). I rs >α×max[I r1 , I r2 , …, I s1 , I s2 , …, I rs ] ···(A)

[0054] Here, α is a predetermined coefficient less than 1, and max[a, b, c] is a function that returns the maximum value of a, b, and c. Therefore, the interference score I rsIf is greater than α times the maximum value of all interference scores associated with RU#r and RU#s, RU#r and RU#s are determined to be neighboring RUs.

[0055] Then, child RU determination section 203 calculates an index of dispersion of the number of connected terminals of the cell when adding a neighboring RU to cell 25-Y, and determines the neighboring RU that minimizes this index as the child RU of cell 25-Y. For the cell with the smallest number of connected terminals, child RU determination section 203 determines one neighboring RU that minimizes the dispersion index of the number of connected terminals of the cell as the child RU, and repeats the determination of child RUs until all RUs 20 belong to one of the cells.

[0056] Next, a connection control method by the connection control device 100 configured as above will be described with reference to the flow chart shown in Fig. 7. In Fig. 7, the same parts as in Fig. 3 are given the same reference numerals, and detailed description thereof will be omitted.

[0057] The received power information reported from each terminal device 30 in the wireless communication system is transmitted from the baseband processing devices 10-1 to 10-M to the connection control device 100 and received by the communication I / F unit 110 of the connection control device 100. Then, the received power for each RU 20 in each terminal device 30 is collected by the received power collecting unit 121 (step S101), and the number of connected terminals for each RU 20 is collected by the connected terminal counting unit 122 from the received power in each terminal device 30 (step S102).

[0058] The interference score calculation unit 201 also calculates interference scores for all pairs of RUs 20 based on the received power at the terminal devices 30 (step S121). That is, the number of terminal devices 30 for which the difference in received power from each RU 20 in each pair is less than a predetermined threshold is counted, and the counted number of terminal devices 30 becomes the interference score for each pair. The interference score calculation process will be described in detail later.

[0059] After the number of connected terminals of each RU 20 is tallied and the interference score of each pair of RUs 20 is calculated, parent RU selection unit 202 selects parent RUs in the same number as cells 25-1 to 25-M (step S122). That is, parent RU selection unit 202 selects M parent RUs based on the number of connected terminals and the interference score of each RU 20. The parent RU selection is performed by selecting the RU 20 with the largest number of connected terminals as the first parent RU, and thereafter selecting the RU 20 with the smallest sum of its interference score with the previously selected parent RU as the next parent RU. The parent RU selection process will be described in detail later.

[0060] Once M parent RUs have been selected, child RU determination unit 203 determines child RUs that belong to the same cell as these parent RUs (step S104). That is, child RU determination unit 203 calculates a dispersion index for the number of terminals connected to the cell when an adjacent RU is added to the cell, and determines the adjacent RU that minimizes the dispersion index as the child RU. The determination of child RUs is repeated until all RUs 20 belong to some cell.

[0061] Because all of the RUs 20 belong to one of the cells 25-1 to 25-M as a result of the parent RU selection process and the child RU determination process, the connection control information generator 125 generates connection control information for connecting the baseband processing devices 10-1 to 10-M to the RUs 20 that belong to the cells 25-1 to 25-M (step S105). The generated connection control information is transmitted from the connection control information transmitter 140 to the connection switching device 50 (step S106), and the connection switching device 50 switches the connections between the baseband processing devices 10-1 to 10-M and the RUs 20 in accordance with the connection control information.

[0062] In this way, each terminal device 30 is set as a connected terminal of the RU 20 with the maximum received power, the RU 20 belonging to each cell is determined so that the dispersion index of the number of connected terminals of the cell is minimized, and the connection relationship between the baseband processing devices 10-1 to 10-M corresponding to the cell and the RU 20 is controlled. As a result, there is no deterioration in the communication quality of the terminal device 30, the variation in the number of connected terminals for each cell is reduced, and the processing load of the baseband processing devices 10-1 to 10-M is averaged. In other words, it is possible to prevent the deterioration of the communication quality in the terminal device 30 while suppressing an increase in the processing load of the baseband processing devices 10-1 to 10-M.

[0063] Next, the interference score calculation process will be specifically described with reference to the flow diagram shown in Fig. 8. The following process is executed by the interference score calculation unit 201.

[0064] Since the interference score is calculated by counting the number of terminal devices 30 that satisfy the conditions for a pair of RUs 20, a process of determining whether to count terminal #i for a pair of RUs #r and #s (r and s are identification information of RUs 20) is repeated. ir and the received power S from RU#s at terminal #i. is It is determined whether the difference between the received powers is less than a predetermined threshold (step S401). If the difference between the received powers is less than the predetermined threshold (step S401 Yes), terminal #i is counted (step S402). If the difference between the received powers is equal to or greater than the predetermined threshold (step S401 No), terminal #i is not counted, thereby obtaining the interference score I rs will be updated.

[0065] Such an interference score I rs This update is repeated for all pairs of RU#r and RU#s, and further repeated for all terminals #i, to calculate interference scores for all pairs of RUs 20. The interference scores for each pair of RUs 20 are stored for the parent RU selection process and the child RU determination process.

[0066] Next, the parent RU selection process will be specifically described with reference to the flowchart shown in FIG. 9. In FIG. 9, the same parts as those in FIG. 4 are denoted by the same reference numerals, and their detailed descriptions are omitted. The following processes are executed by the parent RU selection unit 202.

[0067] First, the first cell's parent RU is selected from the number of connected terminals for each RU20. That is, the RU#r (where r is the identification information of RU20) that satisfies the above formula (1) is selected as the first parent RU#1 (step S201). When the first parent RU#1 is selected, the following processes are repeated according to the number of cells. Here, since the first cell's parent RU#1 is selected, the following processes are repeated for the remaining (M - 1) cells.

[0068] That is, for the c-th cell #c (1 < c ≤ M), the RU#r that satisfies the following formula (6) is selected as the parent RU#c (step S221).

Equation

[0069] However, in formula (6), s is the identification information of the parent RUs of other cells that have already been selected, and I r’s represents the interference score of the pair of RU#r' and RU#s. Therefore, the right side of formula (6) returns r' for which the sum of the interference scores I r’s with the already selected parent RUs is minimized. The process of selecting the RU#r determined by formula (6) as the parent RU#c of cell #c is repeated, and for each of the M cells 25 - 1 to 25 - M, a parent RU is selected. These parent RUs are arranged at positions where the sum of their mutual interference scores is minimized. That is, RUs 20 that are far apart from each other and less likely to interfere are selected as the parent RUs.

[0070] After the parent RU is selected, child RUs belonging to each cell are determined in the same manner as in embodiment 1. That is, a list of neighboring RUs of each cell is generated, and a neighboring RU that minimizes the dispersion index V(r) of the number of connected terminals when added to the cell is determined as the child RU of the cell. In this embodiment, the list of neighboring RUs may be generated by determining that RU#r and RU#s that satisfy the above condition (A) using the interference score are neighboring to each other.

[0071] As described above, according to the present embodiment, the RUs belonging to each cell are determined so that the variation in the number of connected terminals for each cell is minimized, with each terminal device being treated as a connected terminal of the RU with the maximum received power. Therefore, it is possible to average the number of connected terminals of the cells corresponding to each of the multiple baseband processing devices without degrading the communication quality of the terminal device, thereby suppressing an increase in the processing load of the baseband processing device. In addition, since the adjacent relationship between RUs is determined using an interference score based on the received power in the terminal device, it is possible to determine the RUs belonging to each cell even if there is a RU whose location information is unknown.

[0072] (Embodiment 3) A feature of the third embodiment is that, instead of determining the RUs that belong to each cell using the number of terminals connected to each RU, the RUs that belong to each cell are determined using the traffic volume of terminals connected to each RU.

[0073] The configuration of the wireless communication system according to the third embodiment is similar to that of the first embodiment (FIG. 1), and therefore a description thereof will be omitted.

[0074] Fig. 10 is a block diagram showing the configuration of a connection control device 100 according to embodiment 3. In Fig. 10, the same components as those in Fig. 2 are given the same reference numerals, and their explanation will be omitted. The connection control device 100 shown in Fig. 10 has a configuration including a traffic volume counting unit 301, a parent RU selection unit 302, and a child RU determination unit 303, instead of the connection terminal counting unit 122, parent RU selection unit 123, and child RU determination unit 124 of the connection control device 100 shown in Fig. 2.

[0075] The traffic volume counting unit 301 counts the received power from the RU 20 for each terminal device 30, and estimates the connected terminal for each RU 20. Specifically, the traffic volume counting unit 301 identifies the RU 20 with the maximum received power for each terminal device 30, and estimates that each terminal device 30 is a connected terminal of the identified RU 20. Then, the traffic volume counting unit 301 sums up the traffic volumes of the connected terminals of each RU 20, and obtains the traffic volume for each RU 20. Since the traffic volume corresponds to the communication load of the RU 20, it can be said that the traffic volume counting unit 301 counts the estimated communication load for each RU 20 when a connected terminal is connected.

[0076] In this embodiment, traffic volume information of each terminal device 30 is transmitted from the baseband processing devices 10-1 to 10-M and received by the communication I / F unit 110 of the connection control device 100. The traffic volume information is collected by the received power collecting unit 121 together with the received power information. The traffic volume information of each terminal device 30 can be generated from the result of scheduling by the baseband processing devices 10-1 to 10-M. That is, for example, the traffic volume may be the amount of data transmitted from the baseband processing devices 10-1 to 10-M to each terminal device 30 within a predetermined period, or the amount of radio resources allocated to each terminal device 30 by the baseband processing devices 10-1 to 10-M within a predetermined period.

[0077] The parent RU selection unit 302 selects a parent RU for each of the cells 25-1 to 25-M based on the counting result by the traffic volume counting unit 301 and the location information of each RU 20. Specifically, the parent RU selection unit 302 first selects the RU 20 with the largest traffic volume as the parent RU of one cell (e.g., cell 25-1). Then, the parent RU selection unit 302 selects the RU 20 with the greatest distance from the selected parent RU as the parent RU of the next cell (e.g., cell 25-2). Furthermore, the parent RU selection unit 302 selects the RU 20 with the largest sum of distances from the selected parent RU as the parent RU of the next cell (e.g., cell 25-3). In this way, the parent RU selection unit 302 selects the RU 20 with the largest traffic volume as the first parent RU, and then sequentially selects the RUs 20 with the largest sum of distances from the selected parent RU as parent RUs, thereby selecting M parent RUs corresponding to the cells 25-1 to 25-M.

[0078] The child RU determination unit 303 calculates an index of the variation in the traffic volume of the cell, and determines child RUs that belong to the same cell as each of the M parent RUs so that the index is small. Specifically, the child RU determination unit 303 selects a cell with the smallest traffic volume (e.g., cell 25-Y), and identifies adjacent RUs adjacent to RU 20 that already belong to this cell 25-Y. The child RU determination unit 303 then calculates an index of the distribution of the traffic volume of the cell when the adjacent RU is added to cell 25-Y, and determines the adjacent RU that minimizes the index as the child RU of cell 25-Y. Note that the "traffic volume of the cell" is the total of the traffic volumes of all RUs 20 that belong to the cell. For the cell with the smallest traffic volume, the child RU determination unit 303 determines one adjacent RU that minimizes the distribution index of the traffic volume of the cell as the child RU, and repeats the determination of child RUs until all RUs 20 belong to one of the cells.

[0079] Next, a connection control method by the connection control device 100 configured as above will be described with reference to the flow chart shown in Fig. 11. In Fig. 11, the same parts as in Fig. 3 are given the same reference numerals, and detailed description thereof will be omitted.

[0080] The received power information reported from each terminal device 30 in the wireless communication system is transmitted from the baseband processing devices 10-1 to 10-M to the connection control device 100 and received by the communication I / F unit 110 of the connection control device 100. In addition, the baseband processing devices 10-1 to 10-M generate traffic volume information of each terminal device 30 according to the result of scheduling and transmit it to the connection control device 100, and the traffic volume information is received by the communication I / F unit 110 of the connection control device 100.

[0081] Then, the received power for each RU 20 in each terminal device 30 and the traffic volume of each terminal device 30 are collected by the received power collecting unit 121 (step S101). The received power and traffic volume of each terminal device 30 are used to collect the traffic volume by the traffic volume collecting unit 301. That is, the traffic volume collecting unit 301 identifies the RU 20 with the maximum received power for each terminal device 30, and each terminal device 30 is estimated to be a connected terminal of the identified RU 20. Then, the traffic volume collecting unit 301 sums up the traffic volumes of the connected terminals of each RU 20, and collects the traffic volume for each RU 20 (step S141).

[0082] Once the traffic volume of each RU 20 has been tallied, parent RU selection unit 302 selects parent RUs in the same number as cells 25-1 to 25-M (step S142). That is, parent RU selection unit 302 selects M parent RUs based on the traffic volume and location information of each RU 20. Parent RU selection is performed by selecting the RU 20 with the largest traffic volume as the first parent RU, and thereafter selecting the RU 20 with the largest sum of distances from the previously selected parent RUs as the next parent RU. The parent RU selection process will be described in detail later.

[0083] Once M parent RUs are selected, child RU determination unit 303 determines child RUs that belong to the same cell as these parent RUs (step S143). That is, child RU determination unit 303 calculates a dispersion index of the traffic volume of the cell when an adjacent RU is added to the cell, and determines the adjacent RU that minimizes the dispersion index as the child RU. The determination of child RUs is repeated until all RUs 20 belong to one of the cells. The child RU determination process will be described in detail later.

[0084] Because all of the RUs 20 belong to one of the cells 25-1 to 25-M as a result of the parent RU selection process and the child RU determination process, the connection control information generator 125 generates connection control information for connecting the baseband processing devices 10-1 to 10-M to the RUs 20 that belong to the cells 25-1 to 25-M (step S105). The generated connection control information is transmitted from the connection control information transmitter 140 to the connection switching device 50 (step S106), and the connection switching device 50 switches the connections between the baseband processing devices 10-1 to 10-M and the RUs 20 in accordance with the connection control information.

[0085] In this way, each terminal device 30 is set as a connecting terminal of the RU 20 with the maximum received power, the RU 20 belonging to each cell is determined so that the dispersion index of the traffic volume of the cell is minimized, and the connection relationship between the baseband processing devices 10-1 to 10-M corresponding to the cells and the RU 20 is controlled. As a result, there is no deterioration in the communication quality of the terminal device 30, the variation in the traffic volume for each cell is reduced, and the processing load of the baseband processing devices 10-1 to 10-M is averaged. In other words, it is possible to prevent the deterioration of the communication quality in the terminal device 30 while suppressing an increase in the processing load of the baseband processing devices 10-1 to 10-M.

[0086] Next, the parent RU selection process will be specifically described with reference to the flow diagram shown in Fig. 12. In Fig. 12, the same parts as in Fig. 4 are given the same reference numerals, and detailed description thereof will be omitted. The following process is executed by parent RU selection unit 302.

[0087] First, a parent RU of the first cell is selected based on the traffic volume for each RU 20. That is, RU#r (r is identification information of RU 20) that satisfies the following formula (7) is selected as the first parent RU#1 (step S241).

number

[0088] In the formula (7), T RU (r') indicates the traffic volume of RU#r'. Therefore, the right side of equation (7) is the traffic volume T RU The r' with the maximum (r') is returned. When the RU#r determined by formula (7) is selected as the first parent RU#1, the following process is repeated according to the number of cells. In this case, since the parent RU#1 of the first cell is selected, the following process is repeated for the remaining (M-1) cells.

[0089] That is, the process of selecting RU#r as parent RU#c of cell#c using formula (2) above is repeated, and a parent RU is selected for each of M cells 25-1 to 25-M. These parent RUs are placed at positions that maximize the sum of their mutual distances.

[0090] Next, the child RU determination process will be specifically described with reference to the flow diagram shown in Fig. 13. In Fig. 13, the same parts as in Fig. 5 are denoted by the same reference numerals, and detailed description thereof will be omitted. The following process is executed by child RU determination unit 303.

[0091] Here, since the parent RUs of the M cells have already been selected, a cell #c (c is cell identification information) is selected from these cells by the following formula (8) (step S321).

number

[0092] In equation (8), T RU(c') indicates the traffic volume of cell #c'. The traffic volume of cell #c' is the total traffic volume of all RUs 20 that belong to cell #c'. The right-hand side of the above formula (8) is the traffic volume T RU When the cell #c with the smallest traffic volume is selected according to equation (8), a list Nei(c) of RUs adjacent to cell #c is generated (step S302). That is, of the RUs 20 that do not belong to any cell, the RUs 20 that are adjacent to any RU 20 in cell #c are added to the list Nei(c).

[0093] Once the list Nei(c) of neighboring RUs of cell #c is generated, the following process is repeated for each neighboring RU included in the list Nei(c) of cell #c.

[0094] That is, one neighboring RU#r included in list Nei(c) is provisionally added to cell #c (step S303), and the distribution index V(r) of the traffic volume of each cell when this neighboring RU#r is added to cell #c is calculated by the following equation (9) (step S322).

number

[0095] In equation (9), N cell is the number of cells (here M), T RU (c, r) indicates the traffic volume of cell #c when adjacent RU #r is added to cell #c. The dispersion index V(r) calculated by equation (9) is an index of the variation in the traffic volume of each cell when one adjacent RU #r is added to cell #c. Since the traffic volume of a cell is an index of the processing load of the baseband processing device corresponding to this cell, the dispersion index V(r) is also an index of the variation in the processing load of baseband processing devices 10-1 to 10-M.

[0096] In this way, when the dispersion index V(r) when adding an adjacent RU #r to cell #c is calculated for each adjacent RU included in list Nei(c), the adjacent RU #r that satisfies the above formula (5) is added as a child RU of cell #c (step S305). Then, it is determined whether all RUs 20 have been added as child RUs to any cell (step S306), and if there is an RU 20 that does not yet belong to any cell (step S306No), the process is repeated from step S321 where cell #c with the smallest traffic volume is selected.

[0097] Through the above child RU determination process, all RUs 20 belong to one of the cells, and the variation in traffic volume among the cells is minimized. That is, the traffic volume among the cells is averaged, and no baseband processing devices 10-1 to 10-M have an excessive processing load. In other words, an increase in the processing load of the baseband processing devices 10-1 to 10-M can be suppressed.

[0098] As described above, according to the present embodiment, the RUs belonging to each cell are determined so as to minimize the variation in the traffic volume for each cell, with each terminal device being treated as a terminal connected to the RU with the maximum reception power. Therefore, it is possible to average the traffic volumes of the cells corresponding to each of the multiple baseband processing devices, without deteriorating the communication quality of the terminal device, and suppress an increase in the processing load of the baseband processing devices.

[0099] The above-described embodiments can be implemented in appropriate combination. That is, for example, in the third embodiment using the traffic volume for each RU 20, the interference score according to the second embodiment may be used to determine adjacent RUs, and a parent RU may be selected or a child RU may be determined.

[0100] Furthermore, in each of the above embodiments, the connection control device 100 is provided as a separate entity from the connection switching device 50, but the connection control device 100 and the connection switching device 50 may be integrated together. [Explanation of symbols]

[0101] 110 Communication I / F section 120 processors 121 Received power collection unit 122 Connection terminal counting unit 123, 202, 302 Parent RU selection section 124, 203, 303 Child RU Determination Unit 125 Connection control information generation unit 130 Memory 140 Connection control information transmission unit 201 Interference score calculation unit 301 Traffic volume counting unit

Claims

1. An acquisition unit that acquires information on received power from each of a plurality of wireless devices in a plurality of terminal devices; a counting unit that counts an estimated communication load in each of the plurality of wireless devices using the information on the received power; A determination unit that determines a wireless device that belongs to each of a plurality of cells based on an index indicating a distribution of a processing load for each cell corresponding to an estimated communication load of the wireless device in the cell; a generating unit that generates connection control information for connecting a baseband processing device that manages a cell to a wireless device that belongs to the cell; The determination unit is a parent wireless device selection unit that selects a parent wireless device that belongs to each of the plurality of cells based on a positional relationship between the plurality of wireless devices; a child wireless device determination unit that determines whether or not to set a neighboring wireless device adjacent to a cell to which the parent wireless device belongs as a child wireless device belonging to the same cell as the parent wireless device, based on an index indicating a distribution of a processing load for each cell to which the parent wireless device belongs; A connection control device comprising:

2. The tallying unit is The number of connected terminals of each of the plurality of wireless devices is counted when each of the plurality of terminal devices becomes a connected terminal that wirelessly communicates with the wireless device having the largest reception power.

2. The connection control device according to claim 1,

3. The tallying unit is The traffic volume of each of the plurality of terminal devices is tallied when each of the plurality of terminal devices becomes a connection terminal that wirelessly communicates with the wireless device having the largest reception power.

2. The connection control device according to claim 1,

4. The parent wireless device selection unit is A wireless device having a maximum estimated communication load is selected as a parent wireless device belonging to a first cell, and a wireless device having a maximum sum of distances to the selected parent wireless communication devices is selected as a parent wireless device belonging to another cell.

2. The connection control device according to claim 1,

5. The child wireless device determination unit, adding the neighboring wireless devices as child wireless devices of the cell so that an index indicating a distribution of the processing load for each cell is minimized; 2. The connection control device according to claim 1,

6. A calculation unit calculates an interference score indicating a magnitude of interference between the pair of wireless devices by using the information of the received power, The parent wireless device selection unit is The parent wireless device is selected based on a positional relationship between the plurality of wireless devices according to the interference score.

2. The connection control device according to claim 1,

7. A calculation unit calculates an interference score indicating a magnitude of interference between the pair of wireless devices by using the information of the received power, The child wireless device determination unit, The interference score is used to determine whether or not to make the neighboring wireless device the child wireless device.

2. The connection control device according to claim 1,

8. A communication system including a plurality of radio devices that wirelessly communicate with a plurality of terminal devices, a plurality of baseband processing devices connected to the plurality of radio devices, and a connection control device that controls connections between the plurality of radio devices and the plurality of baseband processing devices, The connection control device includes: an acquisition unit for acquiring information on received power from each of the plurality of wireless devices in the plurality of terminal devices; a counting unit that counts an estimated communication load in each of the plurality of wireless devices using the information on the received power; A determination unit that determines a wireless device that belongs to each of a plurality of cells based on an index indicating a distribution of a processing load for each cell corresponding to an estimated communication load of the wireless device in the cell; a generating unit that generates connection control information for connecting a baseband processing device that manages a cell to a wireless device that belongs to the cell; The determination unit is a parent wireless device selection unit that selects a parent wireless device that belongs to each of the plurality of cells based on a positional relationship between the plurality of wireless devices; a child wireless device determination unit that determines whether or not to set a neighboring wireless device adjacent to a cell to which the parent wireless device belongs as a child wireless device belonging to the same cell as the parent wireless device, based on an index indicating a distribution of a processing load for each cell to which the parent wireless device belongs; A communication system comprising:

9. A connection control device Acquire information on reception power from each of a plurality of wireless devices in a plurality of terminal devices; Using the received power information, an estimated communication load in each of the plurality of wireless devices is tallied; determining a wireless device belonging to each of a plurality of cells based on an index indicating a distribution of processing loads for each cell corresponding to an estimated communication load of the wireless device in the cell; Execute a process of generating connection control information for connecting a baseband processing device that manages a cell to a wireless device that belongs to the cell; The process of determining includes: selecting a parent wireless device belonging to each of the plurality of cells based on a positional relationship between the plurality of wireless devices; determining whether or not to treat a neighboring wireless device adjacent to the cell to which the parent wireless device belongs as a child wireless device belonging to the same cell as the parent wireless device, based on an index indicating distribution of processing loads for each cell to which the parent wireless device belongs; 23. A connection control method comprising:

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